how does isolation reflect america at the time of where the crash led to finacinal hardship that affected most vulnurble people

The Great Depression of the 1930's meant massive unemployment. Men had to leave home to find work to feed themselves and their families. Most of the characters in Of Mice and Men exhibit signs of desperate isolation, including those who can be said to have settled into a permanent situation.

Candy, the only other character (aside from Lennie and George) who has an unconditional love for a fellow creature (in Candy's case, his old and feeble dog), is left utterly bereft when Carlson takes his dog out back and shoots it. Candy's immediate attachment to George and Lennie's plan to settle on a farm of their own can be seen as a natural emotional progression following his loss - he looks for new companionship, now that he has lost his poor dog.

Of the other characters, Crooks and Curley's wife also show signs of desperate loneliness, though they respond quite differently. Each is isolated because of special mistreatment. Because Crooks is black, he is shunned by the other men; as we see at the beginning of Chapter Four, he spends his time in his room, alone and bitter. Curley's wife also spends her days hounded by her mean-spirited husband; her attempts to reach out to the other men backfire and win her the (not undeserved) reputation of a flirt.

Both characters, despite their hard and bitter shells, reveal a desire to overcome their loneliness and win friends. Their efforts hinge on Lennie, whose feeble-mindedness renders him unaware of the social stigmas attached to the two. Of course both episodes - Lennie's visit with Crooks in Chapter Four and his talk with Curley's wife in Chapter Five - end (respectively) in bitterness and tragedy. Thus Steinbeck further reinforces the bleakness of life in his fictional world. The one man who could serve as a nonjudgmental companion cannot coexist safely with others.